The present invention relates to the circuit configuration of a semiconductor integrated circuit device, and more particularly, to a circuit configuration of a semiconductor device having a function for converting an output from a sensor, such as a photodiode and, more specifically, for converting a current output to a voltage (I-V conversion), a function for impedance conversion (transimpedance conversion), an amplifying functions, or several types of computing function, and provides a technology for a new high performance and low cost semiconductor integrated circuit device.
FIG. 17 is a circuit diagram showing one example of an I-V conversion circuit. A photodiode (a photodetector, a photodetector and a photodiode are sometimes abbreviated as PD) 17001 is connected in series to an input terminal [-(minus)] 17003 of a differential amplifier (described as an amplifier, a preamplifier, a front-end amplifier, or an operational amplifier) 17005 and is in series with an output terminal 17006 through a feedback resistance (sometimes described as RF). A reference voltage Vs is applied to an input terminal [+(plus)] 17007 thereof.
FIG. 18 is a view of a circuit 18007 showing a conventional type of amplifier (a differential amplifier) and is an example based on the conventional technology of an internal circuit of the differential amplifier (amplifier) shown in FIG. 17 described above.
The conventional type of amplifier has input terminals (-, +) 18004, a Vdd terminal 18001, an output terminal (Vout) 18005, a GND terminal 18008, and a plurality of other elements such as a constant current source 18002, a PNP type of bipolar transistor 18003, and an NPN type of bipolar transistor 18006 or the like, and has a circuit configuration as shown in the figure.
The conventional amplifier circuit has a problem in that current consumption can not be reduced (a base current has to be always flown therein) because it comprises the bipolar transistors as described above. For instance, even if a signal is in the base band at a Vdd of 5 V, the consumed current is around 8 mA when the amplifier is operated at a speed at which signals in the band of 16 MHz can be handled, and around 32 mA, around 4 times larger than that in the former case, when the amplifier is operated at a speed at which signals in the band of 32 MHz can be handled. There is another problem in the conventional type of amplifier in that it is difficult to reduce an operational voltage of an entire circuit to 3 V or below because the amplifier is also driven by a base current (a large V.sub.BEON voltage is required).